Conventional overlay measurement devices rely on optical imaging or scanning inspection to measure the relative positional deviation between two sets of marks. In general, it takes 0.5 to 1 second to position the marks to the center of the field of view of an optical imaging lens and take an image of the marks. With a continuous decrease in device feature sizes and an increase in overlay requirements, more data points need to be taken to improve accuracy of the measurements. It is important to calibrate the position of the wafer during the overlay measurements. It is therefore advantageous to calibrate the wafer position to ensure the accuracy of the overlay measurements.